Schistosomiasis is a major health hazard in many regions of the world. Techniques for the diagnosis of the disease are not yet satisfactory. The aims of this proposal are to isolate and purify a specific enzyme of the adult worm of Schistosoma mansoni and to study its biochemical and immunological properties and to determine its utility in the diagnosis of schistosomiasis. This enzyme is an acidic thiol-dependent proteinase, which may function in the nutrition of the worm, by digestion of host hemoglobin. The enzyme is periodically regurgitated into the host's circulation. The first objective of this proposal is to purify this proteinase to homogeneity, to determine its physical and chemical properties and to obtain specific substrates and inhibitors for the enzyme. The second objective is to determine the utility of the enzyme in the diagnosis of schistosomiasis. Specific proteinase substrates and inhibitors will be used to test chemically for the presence of enzyme in sera. The third objective is to study the role of the proteinase in schistosome physiology and metabolism by determining the appearance of this enzyme during development, and to study its action on specific host proteins including hemoglobin and immunoglobins.